Printing machines



Nov. 29, 1960 M. MOSEGAARD 2,961,953

PRINTING MACHINES Filed Dec. 1, 1958 FIG./. A

2 Sheets-Sheet 1 lnvenlor; mm 7774447416224 By: 5 o w 4 BM ia Attorneys Nov. 29, 1960 M. MOSEGAARD 2,961,953

PRINTING MACHINES Filed Dec. 1, 1958 2 Sheets-Sheet 2 Inventor,-

44M Attorn eys PRINTING MACHINES Marius Mosegaard, Copenhagen, Denmark, assi'gnor to Carl Allers Etablisseme'nt A/ S, Copenhagen, Denmark Filed Dec. 1, 1958, Sky. No. 777,416

Claims priority, application Great Britain May 27, 1958 11 Claims. (Cl. 101-425) This invention relates to offset printing machines and concerns more specially the blanket transfer cylinder which receives an ink impression from a printing cylinder and oifsets or transfers that impression to the material being printed in an impression zone where the material passes over an impression cylinder. The operating surface of such a blanket cylinder is commonly a rubber or some such material which possesses some small degree of resilience which contributes in some part to the desirable form of the image which is imprinted on the material to be printed: in the operation of such machines the surface of the blanket becomes contaminated with a coating of stale or semi-hardened ink and when the material being printed is paper as is most common, the coating includes paper fibres or fluif.

This coating which builds up progressively during a printing run, increasingly impairs the quality of the printed product: attempts have been made to prevent the formationof the coating without stopping the machine, but despite such proposals it is in fact usual and at present indeed necessary to stop the machine from time-to-time to permit the blanket to be washed by an operator, the frequency of the requirement to stop the machine for this purpose depending largely on the nature of the paper being printed in any given run. I I The blankets have to be replaced after certain periods of use for the reason not only that their surface becomes worn, but also because the material loses its essential liveliness and the formation of the coating may well be a contributory factor.

It will be clear therefore that this blanket, while being essential to obtain the particular benefit of oflset printing, is also a major cause of preventing an offset machine from being run continuously at high output speeds due to the necessity for stopping the machine from time-to-time.

It is the main object of the present invention to provide an apparatus by which the surface of the blanket can be maintained in a clean condition without the necessity for 1 stopping the machine at intervals.

According to the present invention, there is provided a mechanical scraping device which comprises a series of strips, most conveniently of metal, which are supported at their ends so that when the strips are applied to the periphery of the transfer cylinder along their length, they are caused to conform to that surface. In this way, the strips will wrap themselves about the periphery of the cylinder and so will have a scraping action over an extended length. In this way also the possibility of the elements digging into the surface of the blanket (as would possibly occur if a strip anchored at one end and free at the other end, were used in the form of a doctor blade), is eliminated.

The scraper can be applied continuously to the blanket 2,961,953 Patented Nov. 2 9, 160

ice

2 l automatically at intervals governed by'the operation. of the machine. t

In addition the scraper can be of dimensions such that will cover the length of the blanket. Alternatively the scraper may have a length which is only a fractional part of the length of the blanket, this scraper (while it is applied to the blanket) being moved lengthwise of itso that '(as the blanket cylinder rotates) the scraping action of the scraper passes progressively over the surface of the blanket thereby avoiding any localized action on theblanket." In the first mentioned case it may be desirable to impart'to the scraper a small longitudinalmovement' again to avoid setting up any local action on the blanket.

It would be preferable to apply the strip elements to the blanket under the action of a resiliency so as to enable the elements the more smoothly to accommodate themselves to the surface of the blanket. I s

It is proposed to remove from the scraper the matter which it has scraped from the blanket by setting up in the operating zone of the scraper a suction which will draw away the matter as it is scraped from the blanket and conduct it to a collecting zone from which it can be removed as necessary.

The scraper can take various constructional forms:v it could comprise a resilient metal sheet stamped out to form a .number of strips extending between marginal lands: the lands could be clamped in a'holder which would so be positioned with respect to the blanket that the strips between the lands lay themselves longitudinally to the curvature of the blanket, when the holder is in its operating position. A similar arrangement could be provided by securing the opposite ends of a series of parallel wires to the holder. ;.v

The cross sectional form of the strips or wires can be such as to provide backed-off edges which will act as blunt cutting edges to shear-off matter from the blanket.

Except in the case in which the scraper has a length which is a part only of the length of the blanket, it is not essential to arrange for movement of the scraper lengthof the blanket.

It has been found that by actual trial that the simple expedient proposed by this invention is not only inexpensive and easy to maintain in operation but does infact enable an offset machine to be run continuously forthe life of the blanket material and at the same time enables clean impressions to be made continuously at high operating speeds. p I V The invention is illustrated by the accompanying drawings in which Figure 1 is a transverse sectional elevation of an oifset printing unit having applied to it one form of scrapper and Figure 2 is a face view of the scraper looking in the direction of the arrow II Figure 1.

Referring to the drawing, a blanket cylinder is shown at 1, a printing cylinder at 2, and an impression cylinder at 3. The cylinders rotates in the directions indicated so that the blanket on the blanket cylinder takes an impression from the printing cylinder 2 and later in its rotation transfers that impression to a web or sheet 4 passing around with the impression cylinder.

The scraper of this invention is shown at 5; this scraper comprises an open holder 6 carried by arms 7 from} rock shaft 8. Across the mouth of this holder is disposed at number of wires '9. ,which are arranged obliquely to the length of the holder: thus by angularly moving the rock shaft 8 the holder can be moved from theinactive position shown in dotted lines (in which the wires are clear of the surface of the blanket) to the active position shown in full lines.

In this active position the wiresfwhich may be either slack or taut in the inactive position of the holder) wrap themselves about the curved periphery of the blanket, the zones of support of the strips 9 at their ends being on chords of the peripheral surface of the blanket cylinder '1. By reason of their obliquity alone, the strips produce the required distributed scraping action on the surface of the blanket as it moves under the wires. The holder 6could be formed of a metal having a sufiicient degree of resiliency as to impose a resilient pull on the wires when the holder 6 is in its active position: in this way, a degree of liveliness is imparted to the scraper constituted by the wires so that the wires accommodate themselves snugly to the form of the surface of the blanket.

It is preferred, as is shown by the drawing, to dispose the holder 6 so that the blanket passes under the scraper wires 9 as it passes from the transfer zone of cooperation with the impression cylinder 3 to the image-receiving zone of cooperation with the printing cylinder 2.

The interior of this holder 6 is connected to a source of suction so that the matter removed by the wires is drawn through the gaps between the wires and away from the holder: in order to localize the suction action to -=the operative zone of the scraper wires blanking plates 10 are mounted on the holder.

The holder 6 is arranged to be moved between the active and inactive positions by an arm 11 which is con- -nected to an arm 12 on the shaft 8 through an overcentre spring 13. This arm 11 can be arranged for actuation by the machine attendant or it can be operated as by being geared to the cylinder drive through a reduction gear so that the holder is moved into active position after the blanket cylinder has made a certain number of rotations.

Where the length of the wire assembly is a part only of the length of the blanket, provision would be made to reciprocate the bracket 14 on which the shaft 8 is carried. This reciprocation action could automatically be rendered active when the arm 11 is operated to apply the scraper wires to the blanket.

1 I claim:

1. A printing machine comprising a rotatable printing cylinder, a rotatable impression cylinder, a rotatable transfer cylinder disposed to receive an impression from the printing cylinder andto transfer it to material passing between itself and the impression cylinder, and in combination therewith, a scraper device for removing matter from the peripheral surface of the transfer cylinder, the said scraper device comprising a series of flexible metallic strip wiper elements supported at zones spaced apart in the lengths of said elements, and means to apply the strips to the peripheral surface of the transfer cylinder at a zone between their zones of support, said strips being wrapped about the said surface and said zones of support being on chords of said peripheral surface.

2. A printing machine comprising a rotatable printing cylinder, a rotatable impression cylinder, a rotatable transfer cylinder disposed to receive an impression from the printing cylinder and to transfer it to material passing between itself and the impression cylinder, and in combination therewith, a scraper device for removing matter from the peripheral surface of the transfer cylinder, the said scraper device comprising a series of strip wiper elements, means resiliently tensioning the elements between their ends, and means to apply the elements laterally to the peripheral surface of the transfer cylinder at a zone between their ends whereby the strips wrap themselves about that surface to give an extended scraping action thereon.

3. A printing machine comprising a rotatable printing cylinder, a rotatable impression cylinder, a rotatable trans fer cylinder disposed to receive an impression from the .4 printing cylinder and to transfer it to material passing between itself and the impression cylinder, and in combination therewith, a scraper device for removing matter from the peripheral surface of the transfer cylinder, the said scraper device comprising a series of flexible metallic strip wiper elements supported in spaced relationship to one another at zones which are spaced in the lengths of said elements and held obliquely to the axis of rotation of the transfer cylinder, and means to apply the strips to the peripheral surface of the transfer cylinder at a zone between their zones of support, said strips being wrapped about the said surface and said zones of support being on chords of said peripheral surface.

4. A printing machine comprising a rotatable printing cylinder, a rotatable impression cylinder, a rotatable transfer cylinder disposed to receive an impression from the printing cylinder and to transfer it to material passing between itself and the impression cylinder, and in combination therewith, a scraper .device for removing matter from the peripheral surface. of thetransfer cylinder, the

said scraper device comprising aseries of strip wiper elements, disposed obliquely to .the axis of rotation of the transfer cylinder, means resiliently tensioning the elements between their ends, and means to apply the elements laterally to the peripheralsurface of the transfer cylinder at a zone between their ends whereby the strips wrap themselves about that surfaceto give an extended scraping action thereon.

5. A printing machine comprising a rotatable printing cylinder, a rotatable impression cylinder, a rotatable transfer cylinder disposed to receive an impression from the printing cylinder and to transfer it to material passing between itself and the impression cylinder, and in combination therewith, a scraper device for removing matter from the peripheral surface of the transfer cylinder, the

said scraper device comprising a series of strip wiper elements supported attheir ends, means toapply the strips to the peripheral surface of the transfer cylinder at a zone between their ends whereby the strips wrap themselves about the said surface, and means to move the scraper in the axial sense of the-transfer cylinder.

6. A printing machine comprising a rotatable printing cylinder, a rotatable impression cylinder, a rotatable transfer cylinder disposed to receivean impression from the printing cylinder and to transfer it to material passing between itself and the impression cylinder, and in combination therewith, .a scraper device for removing matter from the peripheral surface of the transfer cylinder, the said scraper device comprising a series of strip wiper elcments, means resiliently tensioning the elements between their ends, means to apply the elements laterally to the peripheral surface .of the transfer cylinder at a zone between their ends whereby the strips wrap themselves about that surface to give an extended scraping action thereon, and means to move the scraper in the axial sense of the transfer cylinder.

7. A printing machine comprising a rotatable printing cylinder, a rotatable impression cylinder, a rotatable transfer cylinder disposed to receive an impression from the printing cylinder and to transfer it to material passing between itself and the impression cylinder, and in combination therewith, a transfer device for removing matter from the peripheral surface of the transfer cylinder, the said scraper device comprising a series of strip wiper elements disposed obliquely to the axis of rotation of the transfer cylinder, means resiliently tensicning the elements between their ends, means to apply the elements laterally to the peripheral surface of the transfer cylinder at a zone between their ends whereby the strips Wrap themselves about that surface to .give an extended scraping action thereon, and meansto move the scraper in the axial sense of the transfer cylinder.

8. A printing machine comprising a rotatable printing cylinder, a rotatable impression cylinder, a rotatable transfer cylinder disposed to receive an impression from the printing cylinder and to transfer it to material passing between itself and the impression cylinder, and in combination therewith, a scraper device for removing matter from the peripheral surface of the transfer cylinder, the said scraper device comprising a resilient troughed holder, a series of scraper elements in the form of strips secured at their ends to the side walls of the holder, and means to move the holder toward the transfer cylinder to apply the strips to the periphery of the transfer cylinder between their ends, whereby the strips are caused to wrap themselves about the periphery of the transfer cylinder against the resilient loading imposed by the walls of the trough.

9. A printing machine comprising a rotatable printing cylinder, a rotatable impression cylinder, a rotatable transfer cylinder disposed to receive an impression from the printing cylinder and to transfer it to material passing between itself and the impression cylinder, and in combination therewith, a scraper device for removing matter from the peripheral surface of the transfer cylinder, the said scraper device comprising a resilient troughed holder, a series of scraper wires secured at their ends to the side walls of the holder, and means to move the holder toward the cylinder to apply the Wires to the periphery of the transfer cylinder between their ends, whereby the wires are caused to wrap themselves about the periphery of the transfer cylinder against the resilient loading imposed by the walls of the trough.

10. A printing machine comprising a rotatable printing ylinder, a rotatable impression cylinder, a rotatable transfer cylinder disposed to receive an impression from the printing cylinder and to transfer it to material passing between itself and the impression cylinder, and in combination therewith, a scraper device for removing matter from the peripheral surface of the transfer cylinder, the said scraper device comprising a resilient troughed holder interiorly connectable to a source of suction for removing matter scraped by the scraper device, a series of scraper elements in the form of strips secured at their ends to the side walls of the holder, and means to move the holder toward the cylinder to apply the strips to the periphery of the transfer cylinder between their ends, whereby the strips are caused to wrap themselves about the periphery of the transfer cylinder against the resilient loading imposed by the walls of the trough.

11. A printing machine comprising a rotatable printing cylinder, a rotatable impression cylinder, a rotatable transfer cylinder disposed to receive an impression from the printing cylinder and to transfer it to material passing between itself and the impression cylinder, and in combination therewith, a scraper device for removing matter from the peripheral surface of the transfer cylinder, the

said scraper device comprising a resilient troughed holder interiorly connectable to a source of suction for removing matter scraped by the scraper device, a series of scraper wires secured at their ends to the side walls of the holder, and means to move the holder toward the cylinder to apply the wires to the periphery of the transfer cylinder between their ends, whereby the wires are caused to wrap themselves about the periphery of the transfer cylinder against the resilient loading imposed by the walls of the trough.

References Cited in the file of this patent UNITED STATES PATENTS 1,196,437 Doyle Aug. 29, 1916 1,276,163 Biesel Aug. 20, 1918 1,378,278 Roberts May 17, 1921 1,627,774 Goulding May 10, 1927 2,525,982 Westcott Oct. 17, 1950 2,847,935 Richter Aug. 19, 1958 

